Method for manufacturing a rotor

ABSTRACT

A method for manufacturing a rotor includes the following operations: the clamping of a workpiece in a grinding machine; the performance of one or more cylindrical grinding operations whereby a rotor shaft section is ground to the desired diameter with a cylindrical grinding disk; the performance of one more profile grinding operations whereby a rotor body is profiled with a profile grinding disk. During the manufacture of the rotor in the grinding machine, the workpiece is not undamped and the cylindrical grinding operations and the profile grinding operations are done with the same grinding machine.

BACKGROUND

The present invention relates to a method for manufacturing a rotor,such as a rotor for a compressor, a blower, a vacuum pump, or anexpander.

SUMMARY

More specifically the invention relates to such a method that can beused to manufacture a screw rotor for a compressor, a blower, a vacuumpump or an expander.

As is known a rotor of a compressor, a blower, a vacuum pump or expanderconsists of a rotor body that is on a rotor shaft.

The rotor body has a spiral or screw form, for example, with a rathercomplicated profile.

The contours of the rotor body can be mounted between two end faces andwithin an external cylinder casing.

The rotor shaft generally has different cylindrical sections withvarying shaft diameters, such as a section for driving the rotor shaft,sections for fitting bearings, sections for fitting a seal and so on.

At the transition between successive cylindrical sections of the rotorshaft, there are often also radially oriented surfaces that areperpendicular to the rotor axis and which can be important, for exampleas a contact surface for bearings and such.

It is also known that many grinding operations are needed to manufacturesuch complicated shapes, after the preliminary operations (for examplemilling, drilling, turning and/or similar).

These grinding operations can be divided into two major groups.

More specifically the manufacture of the aforementioned cylindricalsections of the rotor shaft or the cylindrical contours of the rotorbody require a number of cylindrical grinding operations.

In such cylindrical grinding operations a multiple oblique or straightinsert grinding technique is generally applied.

For this a cylindrical grinding disk, for example of corundum or CBN, isplaced at an oblique angle or otherwise with respect to the workpiece,and moved one or more times in a direction towards the workpiece, suchthat the profile is copied in the workpiece in a number of places.

As an alternative to insert grinding another cylindrical grindingoperation can also be applied where use is made of a peel grindingtechnology.

With this peel grinding technique, a cylindrical grinding disk can movein any direction so that any shape (diameter, cone, end face, radius)can be worked.

This peel grinding technique is thus much more flexible compared to theinsert grinding technology, as with the same geometry of cylindricalgrinding disk, practically any contour can be worked.

Characteristic of cylindrical grinding disks is the fact that thesecylindrical grinding disks have a rectangular or stepped profile.

Moreover, the end faces of the rotor body and the radially orientedsurfaces of the rotor shaft also require a grinding operation that canbe considered as a shoulder grinding operation, but which for thesimplicity of this text will also be called a cylindrical grindingoperation.

Such a cylindrical grinding operation for the realisation of the endfaces and other radially oriented surfaces can be done by side grinding,whereby a cylindrical grinding disk undergoes a rotation along adirection transverse to the surface to be ground.

This technique is called straight insert grinding.

A more efficient way to grind end faces of the rotor body, or otherradially oriented surfaces on the rotor shaft, consists of moving thegrinding disk towards the surface to be ground in the direction of therotation axis of the grinding disk, so that the side of the grindingdisk grinds the surface concerned.

This last grinding technique is known under the name of cross grinding.

End faces on the rotor body or other radially oriented surfaces on therotor shaft can be most efficiently ground by means of oblique insertgrinding.

The axis of rotation of the grinding disk is in this case at an obliqueangle with respect to the surface to be ground (this angle is generally30°).

A square profile is dressed onto the grinding disk, that is movedperpendicularly to the rotation axis of the grinding disk to theworkpiece, so that an end face or other radially oriented surface, and adiameter of the rotor shaft are ground at the same time.

In order to work on the end faces at both ends of the rotor:

-   -   the rotor must be reversed after doing the first shaft end, or    -   there must be two grinding spindles in the grinding machine that        are mirror images of one another with regard to the insertion        angle

In the aforementioned grinding operations to grind the end faces of therotor body and/or other radially oriented surfaces, a grinding disk canbe used that is identical to the aforementioned cylindrical grindingdisk, which explains why such a grinding operation, more specifically ashoulder grinding operation in the form of a straight or oblique insertgrinding operation or in the form of a cross grinding operation, is alsocalled a cylindrical grinding operation in this text.

To form the profile of the rotor body an entirely different type ofgrinding operation is required, i.e. a profile grinding operation with aprofile grinding disk.

Starting with an unfinished, previously cast or milled workpiece, therotor body is ground into the desired profile during the profilegrinding operation.

Profile grinding disks are used for this purpose, which, as the namesuggests, have an appropriate profile to realise the desirednon-rectilinear profile of the rotor body.

This profile is for example typically a curved profile for therealisation of the spiral for rotors of a screw compressor, a blower, avacuum pump or an expander.

The profile grinding operation to grind the profile of the rotor body,in which a spiral worm grinding disk is used is often also called a hobgrinding operation in the trade.

In this text all grinding operations that are intended to realise thespiral profile of the rotor body are called profile grinding operations,and the grinding disk used a profile grinding disk.

According to the known methods for manufacturing a rotor for acompressor, a blower, a vacuum pump, an expander, the cylindricalgrinding operations (including the grinding operations for the end facesof the rotor body and for other radially oriented surfaces of the rotorshaft) and the profile grinding operations are done on differentgrinding machines, whereby all cylindrical grinding operations areusually done first on a cylindrical grinding machine and then theprofile grinding operations on a profile grinding machine.

Disadvantages of an economic nature are attached to these known methods,as well as with regard to the quality yielded.

First and foremost two different types of grinding machine, that use adifferent technology, have to be purchased and maintained, which is ofcourse an expensive matter.

Moreover, such grinding machines occupy a lot of space, which can meanan additional cost.

The setting up and adjustment of the two types of grinding machine formanufacturing a certain rotor require a lot of work.

Moreover, every workpiece first has to be clamped (one or more times) ina cylindrical grinding machine, and then taken from this cylindricalgrinding machine after doing the cylindrical grinding operationsconcerned, and then clamped in a profile grinding machine to do theprofile grinding operations to form the rotor.

All these steps require a lot of labour and time, such that the leadtime for manufacturing a rotor is considerable.

Another disadvantage attached to this is that there is a considerabledifference between the time that a workpiece spends in a cylindricalgrinding machine and the time that this workpiece spends in a profilegrinding machine during the manufacture of the rotor.

This means that the capacities of the two types of machine are notutilised to a maximum, which also constitutes an economic loss.

For the people who have to operate the grinding machines, working withtwo types of grinding machine also requires an intensive form oforganisation.

The operating panels of the cylindrical grinding machines differ fromthe operating panels of the profile grinding machines to such an extentthat as a rule these operations cannot be done by the same operators.

With regard to the quality of the rotor finish, the known methods havethe first big disadvantage that the workpiece to be ground has to beclamped in a grinding machine a number of times, whereby errors canaccumulate and the risk of damage increases.

Indeed, for the good performance of the rotor to be manufactured, it isof paramount importance that the rotor profile is manufactured with avery high degree of accuracy.

More specifically the rotor profile must be very well aligned withrespect to the centre line through the sections of the rotor shaft thatare used for fitting the supporting bearings.

Because in the known methods these sections of the rotor shaft for thebearings and the profile of the rotor body are manufactured on differentmachines, clamping errors inevitably occur that are not conducive to theaccuracy with which the profile of the rotor body is manufactured.

To clamp the workpiece in the different types of grinding machine,(prior to the cylindrical grinding operations) centre holes are made atboth ends of the rotor and the workpiece is clamped in between one orboth centre points provided on the grinding machine.

To clamp the workpiece in the grinding machine, in conventional profilegrinding machines, a centre point of the grinding machine is only put inthe centre hole concerned at one end of the workpiece.

At the other end the workpiece is clamped on a cylindrically ground partof the shaft.

For an accurate finish of the rotor, in the known methods it is thusextremely important that the centre holes are made very accurately.

However, even with an extremely accurate implementation of the centreholes, clamping errors are inevitable due to the multiple clamping ofthe workpiece.

In addition, every machine has geometric anomalies that also result inerrors when working the workpiece, and thus result in a poorer finishand/or lower quality of the rotor.

As the geometric anomalies differ in the machines for the successiveoperations, in the known methods these errors accumulate during theprocessing of the workpiece.

Moreover, there is a substantial risk that the workpiece is damaged bybeing clamped a number of times, for example the functional parts of therotor, but also the aforementioned centre holes.

Another disadvantage of the known methods for manufacturing a rotor of acompressor, a blower, a vacuum pump, or an expander, that is detrimentalto the quality relates to the order of operations.

Indeed, in the known methods all cylindrical grinding operations aredone first, because the sections of the rotor shaft that support thebearings are also manufactured with cylindrical grinding operations.

One of these sections of the rotor shaft is also used to centre, clampand drive the rotor for the profile grinding, which is necessary becauselarge forces are generated during profile grinding.

When profile grinding a rotor for a screw compressor, blower, vacuumpump, or expander, one or more coarse profile grinding operations arefirst done on the workpiece to grind the spiral grooves in the rotorbody.

A substantial proportion of the grinding power here is converted intoheat that accumulates in the workpiece.

This heat accumulation in the workpiece negatively affects certain partsof the workpiece that have already been cylindrically ground, such asthe end faces of the rotor body or for example the cylindrical peripherythat encloses the contour of the rotor body.

Another disadvantage attached to the order of operations followed inknown methods consists of the coarse profile grinding operation beingimmediately followed by a fine profile grinding operation, whereby theaforementioned heat that has accumulated in the workpiece is onlygradually dissipated during this fine profile grinding operation.

A consequence of this is that, as a result of the temperature change,the dimensions of the workpiece change during fine grinding and thus theprofile of the rotor body is not made evenly over the rotor body.

In brief, in a rotor of a screw compressor, a blower, a vacuum pump, oran expander, this can mean for example that the grooves in the rotor arenot made uniformly.

Furthermore, when coarse profile grinding the workpiece large burrs canoccur at the edges of the end faces of the rotor body and/or thecylindrical contour wall of the rotor body that are not generallyremoved by simple machine brushing away.

In the known methods there is thus a considerable risk that, whenremoving these large burrs, damage is caused to the finely ground partsalready made by the cylindrical grinding of the rotor, such as theaforementioned end faces or the contour of the rotor body, which arecritical parts for the good performance of the rotor.

In the known methods, these large burrs generally have to be removedmanually and with great care, which is a delicate process and thus takesup a non-negligible amount of time.

The handling and manual deburring of rotors with such large burrs alsomeans substantial risks of injury.

If both grinding operations (cylindrical grinding and profile grinding)are done with CBN grinding disks, for example when high productivitygrinding techniques are used, these grinding operations are generallydone with oil, which constitutes an additional safety risk.

Indeed, with oil spills on the production floor the risk of slippingincreases substantially, and as in the known methods the workpieces haveto be taken one or more times from a cylindrical grinding machine to aprofile grinding machine, the risk of oil spills in the known methods isvery real.

With the current known methods for manufacturing a rotor for acompressor, blower, vacuum pump, or expander, during the cylindricalgrinding and profile grinding the workpiece is driven at one end, andwhen clamping the workpiece in the grinding machine at the other, notdirectly driven end of the workpiece, a fixed centre point is generallyused that engages in a centre hole in the end of the workpiececoncerned.

Consequently there is a big risk that the centre hole at theaforementioned end of the workpiece is damaged by friction during theoperation, which can also have a detrimental effect on the quality ofthe rotor manufactured in subsequent operations.

The purpose of the present invention is thus to provide a solution tothe aforementioned disadvantages and any other disadvantages.

To this end the invention concerns a method for manufacturing a screwrotor for a compressor, a blower, a vacuum pump or an expander, that atleast comprises the following operations:

-   -   the clamping of a workpiece, that has already been partially        processed so that it already has the shape of a rotor, in a        grinding machine to perform a grinding operation;    -   the performance of one or more cylindrical grinding operations,        whereby in such cylindrical grinding with a cylindrical grinding        disk, one or more sections of the workpiece are pre-ground to        the desired diameter to form a rotor shaft section;    -   the performance of one more profile grinding operations, whereby        in such profile grinding with a profile grinding disk, a section        of the workpiece is profiled to form a rotor body of the screw        rotor;        and such that, during manufacture of the screw rotor in the        grinding machine, the workpiece is not unclamped and both the        cylindrical grinding operations and the profile grinding        operations are done with the same grinding machine.

A great advantage of the method according to the invention formanufacturing a rotor consists of only having to clamp the workpieceduring the manufacture of the rotor once, and it is not unclamped untilthe entire rotor has been finished.

This increases the quality yielded because no clamping errors can occurdue to the workpiece being clamped a number of times, as is the casewith the known methods.

As all grinding operations are done in the same grinding machine, noerrors accumulate as a result of geometric anomalies in the machine.

Moreover, in a method according to the invention, the risk of damagebeing caused to the workpiece is reduced, compared to the risk of damagewith the known methods, as the workpiece no longer has to be clamped anumber of times.

The accuracy with which the centre holes are realised on the workpiecefor its clamping in the grinding machine is also less important in amethod according to the invention than in the known methods, as duringthe entire manufacture of the rotor the workpiece remains clamped in thegrinding machine and thus all operations are automatically centredaround the centre points on the grinding machine, between which theworkpiece is clamped in.

With a method according to the invention, the entire series ofoperations is done in one grinding machine, which has many advantages.

First of all the investment to be made is less and the space requiredfor grinding machines is less than with the known methods.

The capacity of the grinding machine used can also be fully utilised.

A step-by-step capacity expansion is possible and this leads to a morepredictable investment policy over time.

Moreover, only one grinding machine has to be set up beforehandaccording to the type of workpiece that has to be manufactured.

In addition, no further time is lost by exchanging workpieces betweendifferent machines.

When the method according to the invention is applied on two grindingmachines simultaneously, that each can do cylindrical grindingoperations and profile grinding operations, the production process isless sensitive to production loss as a result of machine faults or as aresult of the conversion of one of the machines, compared to thesituation with the known methods where one cylindrical grinding machineand one profile grinding machine are used.

Indeed, when according to the known methods for manufacturing a rotor,separate grinding machines are used for the cylindrical grinding andprofile grinding, then the production flow is interrupted as soon as oneof the two grinding machines has a fault or is converted, such that theentire production capacity is immediately lost.

The degree of utilisation of the grinding machine is thus greater in amethod according to the invention than in the known methods.

The process time during which a workpiece remains in one grindingmachine is much greater than with the known methods, such that anoperator can easily operate a number of grinding machinessimultaneously.

The total time required for manufacturing a rotor is thus substantiallyreduced with a method according to the invention.

According to a preferred method according to the invention, whenmanufacturing a rotor a universal grinding spindle of the grindingmachine is used whereby a grinding disk is taken off the universalgrinding spindle after performing a grinding operation and anothergrinding disk is put on this universal grinding spindle to perform asubsequent grinding operation.

Preferably this exchange of grinding disks is done automatically.

An advantage of this preferred method according to the inventionconsists of the aforementioned universal grinding spindle being utilisedto the optimum.

Such a preferred method according to the invention enables rotors ofboth the female type and complementary rotors of the male type to bemanufactured in some cases, without having to convert the grindingmachine, which also means a significant time saving and whereby forexample male and female rotors for screw compressors can be manufacturedin pairs in one grinding machine.

This means a substantial advantage as the lead time for producing arotor set and a compressor element is substantially reduced as a result.

This is very important as a compressor element can only be assembledwhen both rotors are available.

According to another preferred method according to the invention,between two grinding operations a flushport or set of flushports canalso be exchanged.

Such flushports can be used to obtain optimum cooling, to extinguishsparks, or to clean the grinding stone during grinding.

Depending on the circumstances, when the geometry of the grindingmachine is changed, it can be chosen to exchange or reposition only onesuch flushport or an entire set of such flushports with their specificfunction.

Such a preferred method provides the advantage that the conversion timescan be substantially reduced, such that the periods in which productionhas stopped is reduced.

Moreover, grinding disks and flushports can be exchanged without havingto stop the grinding machine.

According to a greatly preferred method according to the invention,after the first coarse profile grinding operation to obtain a workpiecewith a coarsely ground rotor body, one or more interim cylindricalgrinding operations are done to grind one or more rotor shaft sections,an external diameter of the rotor body and/or one or both end faces ofthe rotor body, after which the profile of the rotor body is finelyground during a fine profile grinding operation.

Such a method according to the invention solves the aforementionedproblems of the known methods that are the result of the heataccumulation in the workpiece during the coarse profile grinding of therotor body, as well as the formation of large burrs from this coarseprofile grinding of this rotor body.

Indeed, with this preferred method according to the invention, theprofile of the rotor body is first coarsely ground by profile grinding,whereby the large burrs that occur as a result of this coarse profilegrinding can be removed during a subsequent fine cylindrical grindingoperation.

This can be done by fine grinding the outside diameter and end faces ofthe rotor body by cylindrical grinding, in order to finally fine grindthe profile of the rotor body in a fine profile grinding operation.

A first important advantage is that the burrs are removed by thecylindrical grinding of the critical parts of the rotor body, such thatthere is less risk of damage when removing the small burrs that occurwhen fine profile grinding the profile.

In contrast to the large burrs from the coarse profile grinding of therotor body, these fine burrs can easily be removed with machinebrushing.

These fine burrs can be removed in the same machine, for example byreplacing a grinding disk on an aforementioned universal grindingspindle with a deburring brush.

Moreover, the workpiece has cooled down when the profile of the rotorbody is finally fine ground.

In the known methods in which different grinding machines are used forcylindrical grinding and profile grinding, such an order of theoperations is impossible or at least very disadvantageous, as far toomuch time is lost changing machines, and each time the workpiece isclamped in a grinding machine clamping errors accumulate.

BRIEF DESCRIPTION OF THE DRAWINGS

With the intention of better showing the characteristics of theinvention, a preferred method and grinding machine according to theinvention is described hereinafter by way of an example, without anylimiting nature, with reference to the accompanying drawings, wherein:

FIG. 1 shows a side view of a rotor of a screw compressor;

FIG. 2 schematically illustrates a first cylindrical grinding operation,more specifically the oblique multiple insert grinding with acylindrical grinding disk;

FIG. 3 schematically illustrates a top view of a cylindrical grindingoperation, more specifically peel grinding with a cylindrical grindingdisk;

FIGS. 4 and 5 show a cross-section of two possible profile grindingdisks (intended for profile grinding a male and female rotor of a screwcompressor respectively);

FIGS. 6 and 7 schematically illustrate the first two steps of a methodaccording to the invention for manufacturing a rotor according to FIG.1, whereby a cylindrical grinding operation is applied in these steps;

FIGS. 8 and 9 each schematically illustrate a front view of a next stepof a method according to the invention to manufacture a male or femalerotor of a screw compressor respectively, in which a coarse profilegrinding operation is performed;

FIG. 10 illustrates a subsequent step of the method according to theinvention in which a number of cylindrical grinding operations are done;

FIGS. 11 and 12 illustrate, analogous to FIGS. 8 and 9, the fine profilegrinding of a male and female rotor for a screw compressor respectively;

FIG. 13 illustrates a last cylindrical grinding operation of the method;

FIGS. 14 and 15 show two possible embodiments of a grinding machineaccording to the invention; and

FIG. 16 schematically shows a side view of a set of flushports of thegrinding machine.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The rotor 1 shown in FIG. 1 is a male type rotor 1 for a screwcompressor, that consists of a rotor shaft 2 on which there is a rotorbody 3.

The rotor body 3 can be contained in a cylindrical body that has anoutside diameter D.

The axial ends of the rotor body 3 are formed by two end faces 4 and 5,whereby upon assembly of the rotor 1 in the screw compressor, the endface 4 is specifically intended to be oriented towards an outlet side,while the end face 5 is intended to be oriented towards an inlet side ofthe compression chamber of the screw compressor.

As the rotor body 3 is intended for compressing or expanding air oranother medium in a compressor, vacuum pump or expander, it also hasspiral 6, whereby the teeth 7 are separated from one another by grooves8.

The rotor shaft 2 consists of different sections with varying diameters,both on the inlet shaft side and on the outlet shaft side.

In the example shown, at one end of the rotor shaft 2 there is asuitable section 9 for driving the rotor shaft 2.

Moreover, on each side of the rotor body 3 there is a section forsupporting the rotor shaft 2 while rotating with respect to a housing ofa screw compressor by means of a bearing, sections 10 and 11respectively.

In the example shown, adjacent to the section 10 for a bearing of therotor shaft 2 there is a certain step to form an axial contact surface12 that is perpendicular to the axis AA′ of the rotor 1, and which canact as an axial contact surface 12 for the bearing to be fitted.

Moreover, between sections 10 and 11 for the bearings and the rotor body3, there is also a section for sealing the rotor 1 in the housing of thescrew compressor, sections 13 and 14 respectively.

To clamp and centre the rotor shaft 2 in a grinding machine, there is acentre hole 17 centrally in both ends 15 and 16 of the rotor shaft 2.

It is clear that this complicated shape requires a multitude ofdifferent operations.

More specifically the different sections 10 to 14 of the rotor shaft 2,and the external diameter D of the rotor body 3, are obtained byperforming a number of cylindrical grinding operations.

By way of an example, FIG. 2 illustrates such a cylindrical grindingoperation, more specifically the multiple oblique insert grinding with acylindrical grinding disk 18.

Such a cylindrical grinding disk 18 generally has an abrasive such ascorundum or CBN (Cubic Boron Nitride) and has a typical cutting profile19.

In the case of FIG. 2, the cutting profile 19 is such that when thecylindrical grinding disk 18 is obliquely inserted, a part of a shaftcan be ground to a certain diameter and a radially oriented surface canbe ground on this shaft at the same time.

In this case the workpiece is a shaft 20 that undergoes a rotarymovement around its axis BB′ and in which the stepped cutting profile 19of the cylindrical grinding disk 18 is copied a number of times bymoving the cylindrical grinding disk 18, which in this example rotatesaround the oblique axis CC′, towards the shaft 20 along the obliquedirection DD′ during the insert grinding.

In this way the shaft 20 can be given a stepped profile.

Another form of cylindrical grinding shown in FIG. 3, more specificallya peel grinding operation whereby a part of a shaft 21 is ground to acertain diameter with a cylindrical grinding disk 18.

In contrast to what was the case with the insert grinding, when peelgrinding the cylindrical grinding disk 18 only undergoes a small feedmovement in the direction of the shaft 21, and the further peel grindingis done by moving the rotating cylindrical grinding disk 18 in thelongitudinal direction EE′ parallel to the shaft direction FF′.

To realise the end faces 4 and 5 of the rotor body 3, and possibly thecontact surface 12 between the rotor shaft sections 10 and 13 (see FIG.1), a grinding operation is required, for example by grinding with agrinding disk end on to the end faces 4 and 5 or the contact surface 12.

A cylindrical grinding disk 18 can also be used for this grindingoperation, for example of the type as shown in FIG. 3, and hereinaftersuch a grinding operation shall also be considered as a cylindricalgrinding operation.

To realise the spiral toothing 6 of the rotor body 3 another grindingoperation is needed, i.e. a profile grinding operation using a profilegrinding disk 23, a few examples of which are shown in FIGS. 4 and 5.

It is clear that these profile grinding disks 23 have a profile 24 thatcorresponds to the profile of the spiral grooves 8 of the rotor body 3.

Moreover, the grinding of the spiral toothing 6 requires a combinedmovement of the workpiece and the profile grinding disk 23 that is muchmore complicated than with cylindrical grinding.

According to the known methods, the cylindrical grinding and profilegrinding are done on different grinding machines, which leads to anumber of disadvantages, as set out in the introduction.

The steps that a method according to the invention preferably containsare set out below.

It is of great importance here that in such a method according to theinvention, only one grinding machine is used and that the workpiece isnot unclamped during the manufacture of the rotor 1.

FIG. 6 shows a first step of the method, whereby a workpiece 25, thathas already been partially processed for example and more or lessalready has the shape of a rotor 1 as shown in FIG. 1, is clamped byclamping the workpiece 25 in between the two centre points 26 of thegrinding machine 27.

After clamping the workpiece 25 between the two centre points 26, afirst cylindrical grinding operation is preferably done with acylindrical grinding disk 18 of the grinding machine 27, which consistsof cylindrically grinding the section 10 at the end 15 of the workpiece25, to obtain a cylindrical clamping surface 28 that is centred withrespect to the centreline GG′.

It is clear that for the good removal of the ground material and/or toobtain a certain cooling and lubrication of the workpiece 25 duringgrinding, it is best to use a flushport 29 or a set of flushports 28.

It can also be the intention to extinguish sparks that occur duringgrinding with such a flushport 29.

FIG. 16 shows a typical configuration in which a set of flushports 29 isused to cool, lubricate and clean the grinding disk 18 and the workpiece25, and to extinguish sparks that occur during grinding.

The flushport 29 to provide cooling and lubrication is placed above thecontact zone between the cylindrical grinding disk 18 and the workpiece25.

This cooling port 29 for cooling and lubrication is oriented in thedirection of rotation of the grinding disk to the aforementioned contactzone between the cylindrical grinding disk 18 and the workpiece 25.

The flushport 29 that is intended to extinguish sparks is oriented in adirection opposite to the direction of rotation of the cylindricalgrinding disk 18 and towards the aforementioned contact zone between theworkpiece 25 and the cylindrical grinding disk 18.

Finally there is a further flushport 29 for cleaning the cylindricalgrinding disk 18 that is oriented to a part of the grinding disk 18 in adirection perpendicular to the surface of the grinding disk 18.

When turning the grinding disk 18, a part of the grinding disk 18 willfirst be cleaned at the flushport 29 concerned, after which this partcomes into contact with the workpiece 25 whereby it is lubricated toreduce the development of heat, and whereby the heat released by thegrinding is dissipated by cooling and any sparks that occur areextinguished with the flushports 29 concerned.

Of course the same set of flushports 29 can be provided during theprofile grinding, and more or fewer flushports 29 can be used and/orconfigured differently.

In a subsequent step of the method according to the invention, shown inFIG. 7, the workpiece 25 is first additionally clamped with a clampingmechanism or clamping system 30, that moves towards the workpiece, ofthe grinding machine 27 that engages around the clamping surface 28formed in the previous step.

Moreover, a section 11 at the other end 16 of the workpiece 25, forexample a section 11 intended for fitting a bearing, but othercomponents are not excluded, is cylindrically ground with a cylindricalgrinding disk 18 of the grinding machine 27, either the same cylindricalgrinding disk 18 or a different cylindrical grinding disk 18 than in theprevious step, to form a cylindrical support surface 31 that is centredwith respect to the centre line GG′.

FIGS. 8 and 9 show a subsequent step of the method according to theinvention, whereby a coarse profile grinding operation is performed togrind a first coarsely finished spiral toothing 6 of the rotor body 3,respectively for grinding a male rotor 1 and a female rotor 1 of a screwcompressor.

To perform a profile grinding operation, the workpiece 25 has to befully supported at the end 15, whereby it is driven during grinding.

To this end, the workpiece 25 is at least clamped between the centrepoints 26 and clamped in with a clamping mechanism or clamping system 30at the end 15.

If desirable for stability, the other end 16 of the workpiece 25 issupported in a rotating way by means of a stay 32 supported on bearingsor a sliding stay 32 that is fitted around the support surface 31 groundin the previous step.

In this way the workpiece 25 is sufficiently supported to accommodatethe large forces that occur during the profile grinding and/or toprevent or limit the bending of the workpiece 25 during the profilegrinding.

To perform the profile grinding operation, a profile grinding disk 23 ofthe grinding machine 27 is of course used.

It is important to note that, in contrast to what is the case in theknown methods, here it is a profile grinding disk 23 of the samegrinding machine 27.

The only difference between FIGS. 8 and 9 relates to the orientation ofthe profile grinding disk 23 in the grinding machine 27, whichdemonstrates that with the same grinding machine 27 both a female andmale rotor 1 for compressors, blowers, vacuum pumps, or expanders, canbe easily manufactured, just by changing the orientation of the profilegrinding disk 23.

After this first coarse profile grinding operation to obtain a workpiece25 with a coarsely ground rotor body 3, according to the invention, oneor more interim cylindrical grinding operations are preferablyperformed, as illustrated in FIG. 10.

Such cylindrical grinding operations can consist of cylindricallygrinding one or more rotor shaft sections, such as the fine cylindricalgrinding of the sections 10 to 14 or the external diameter D of therotor body 3.

In such interim cylindrical grinding operations, one or both end faces 4and 5 of the rotor body 3 are finely ground.

For these interim grinding operations, a cylindrical grinding disk 18 ofthe grinding machine 27 is again used.

The advantages of performing these interim grinding operations primarilyconsist of the fact that the fine grinding of the parts concerned isonly done after the profile of the rotor body 3 has already been groundinto its rough shape, so that the negative effects of the coarse profilegrinding, such as the accumulation of heat in the workpiece 25,deburring, and so on, can no longer affect the finish of the rotor 1.

According to a preferred method according to the invention, one of thesteps consists of a deburring operation with the same grinding machine27.

The large burrs can be deburred, for example, by cylindrical grindingthe end faces 4 and 5 of the rotor body 3 and/or the outside diameter Dof the rotor body 3.

In a subsequent step of the method, the spiral toothing 6 of the rotorbody 3 can be finely ground using a profile grinding disk 23 with a finegrain and accurate profile.

This is shown in FIGS. 11 and 12, again for manufacturing a male andfemale rotor 1 respectively for a screw compressor.

In a subsequent step of the method, the finely ground spiral toothing 6can be deburred, for example, by removing the fine burrs with adeburring brush 40.

Finally, in a last step of the method according to the invention, theclamping mechanism or clamping system 30 can be opened and pulled backand the supporting stay 32 removed, after which the clamping surface 28can be finely ground in a last grinding operation by cylindricalgrinding with a cylindrical grinding disk 18 of the grinding machine 27to form a finely ground section 10 for fitting a bearing.

It is clear that in this way a rotor 1 can be manufactured withouthaving to unclamp the workpiece 25, which brings about the intendedadvantages as set out in the introduction.

In summary it can be said that a method according to the inventionpreferably comprises the following steps whereby the following order ofoperations is preferably followed:

-   -   the cylindrical grinding of a clamping surface 28 for a clamping        mechanism or clamping system 30;    -   the cylindrical grinding of a support surface 31 for a stay 32;    -   the coarse profile grinding of the rotor body 3;    -   the cylindrical grinding of one or both end faces 4 and 5 of the        rotor body 3, whereby the large burrs on both surfaces are at        least partially removed at the same time;    -   the cylindrical grinding of the less critical shaft diameters of        the rotor 1;    -   the cylindrical grinding of the bearing surfaces 10 and 11;    -   the cylindrical grinding of the outside diameter D of the rotor        body 3, whereby the large burrs are at least partially removed        at the same time;    -   the fine profile grinding of the rotor body 3, the fine        cylindrical grinding of the clamping surface 28 for the clamping        mechanism or clamping system 30, or in other words the section        10 at the end of the rotor shaft 2.

Of course the application of another order of operations and/or theaddition of operations and/or elimination of operations, are notexcluded according to the invention.

According to a preferred method according to the invention the method isat least partially automated.

According to the invention use can be made of a grinding machine 27 tomanufacture a rotor of a compressor, an example of which is shown inFIG. 14.

This grinding machine 27 has clamping means in the form of centre points26 and a withdrawable clamping mechanism or clamping system 30 forclamping a workpiece 25, but they can just as well take on another form.

Moreover, the grinding machine 27 has one universal grinding spindle 33and a number of exchangeable cylindrical grinding disks 18 and a numberof exchangeable profile grinding disks 23, as well as a number ofdeburring brushes 40, that are contained in a magazine 34 of anautomated exchanger 35 of the grinding machine 27.

There are also a number of exchangeable flushports 29 or a number ofsets of exchangeable flushports 29 in the magazine 34 of the exchanger35, that may or may not be exchanged at the same time with the grindingdisk 18 or 23.

During the manufacture of a rotor 1, the tool exchanger 35 is intendedto affix the exchangeable grinding disks 18 or 23, or the deburringbrushes 40, from the magazine 34 to the universal grinding spindle 33 ofthe grinding machine 27 or vice versa.

In this way a method according to the invention can be applied whereby agrinding disk, either a cylindrical grinding disk 18 or a profilegrinding disk 23, or a deburring brush 40, is removed from the universalgrinding spindle 33 after performing an operation and another tool,either a cylindrical grinding disk 18, a profile grinding disk 23, or adeburring brush 40 is placed on this universal grinding spindle 33 toperform a subsequent grinding operation.

Preferably a flushport 29 or a set of flushports (for example, accordingto FIG. 16) is also exchanged between two grinding operations, oralternatively such a flushport 29 or set of flushports 29 can just bepositioned differently.

Moreover, the grinding machine 27 has a control 36 for automaticallyperforming grinding operations for the manufacture of the rotor 1.

FIG. 14 schematically presents this control 36, but such a control 36can for example consist of a computerised system for controlling alltypes of motors 37 of the universal grinding spindle 33, or robot armsfor moving grinding disks 18 and 23, and/or deburring brushes 40 and/orflushports 29 and so on.

To close, the grinding machine 27 also has switching means 38 thatenable switching between at least two operating modes, more specificallybetween a first operating mode for grinding with a cylindrical grindingdisk 18 and a second operating mode for grinding with a profile grindingdisk 23, all such that the workpiece 25 does not have to be unclampedfor the changeover between the possible operating modes.

The switching means 38 preferably enables the grinding machine 27 toswitch to an additional operating mode for deburring a workpiece 25 witha deburring brush 40.

The switching means 38 and the tool exchanger 35 can again be realisedin a thousand and one ways according to the arts of automation, and arepreferably controlled by the control 36.

The grinding machine 27 also preferably has one or more positionableand/or exchangeable flushports 29 or set of flushports 29 that are alsocontrolled by the control 36.

FIG. 15 shows another embodiment of a grinding machine 27.

This grinding machine 27 has one or more task-specific grinding spindles39 that each have a specific grinding disk, either a cylindricalgrinding disk 19 or a profile grinding disk 23, and an appropriateflushport set 29.

The grinding machine 27 also has one or more separate deburring brushes40 that is or are placed on a deburring brush spindle 41 suitable forthis purpose.

Moreover, this grinding machine 27 has a control 36 and switching means38 for switching between the different operating modes, as in theprevious case.

The intention here is that during the manufacture of a rotor 1, thecontrol 36 controls a task-specific grinding spindle 39 or a deburringbrush spindle 41 without a specific grinding disk 18, 23 or deburringbrush 40 being exchanged on its task-specific grinding spindle 39 ordeburring brush spindle 41 concerned.

In this way a method according to the invention can be realised in whicha first grinding operation is performed using a first specific grindingdisk 18 or 23 that is mounted beforehand on a first task-specificgrinding spindle 39 of the grinding machine 27, and a second grindingoperation is performed using a second specific grinding disk 18 or 23that is mounted beforehand on a second task-specific grinding spindle 39of the grinding machine 27 and/or a deburring operation is done using adeburring brush 40 that is mounted beforehand on a deburring brushspindle 41 of the grinding machine 27.

Preferably in such a method, both for the aforementioned first andsecond grinding operations, a flush is applied by making use of a firstand second flushport or set of flushports 29 respectively, and thesefirst and second flushports or set of flushports 29 are mounted on thegrinding machine 27 beforehand such that a flush can be projected to theworkpiece 25 in the vicinity of the first and second grinding disk 18and/or 23 respectively.

It is clear that the ideas behind the embodiments of FIGS. 14 and 15 canbe combined by combining one or more universal grinding spindles 33 withone or more task-specific grinding spindles 39 and/or deburring brushspindles 41 in one grinding machine 27.

The present invention is by no means limited to the method formanufacturing a screw rotor 1 of a compressor, a blower, a vacuum pump,or an expander, described as an example and illustrated in the drawings,but such a method according to the invention can be realised in allkinds of variants, without departing from the scope of the invention.

The invention claimed is:
 1. A grinding machine for manufacturing arotor of a compressor, the grinding machine comprising: a clampingsystem that clamps a workpiece; a grinding spindle; one or moreinterchangeable cylindrical grinding disks including a first cylindricalgrinding disk configured to be affixed and removed from the grindingspindle; two or more interchangeable profile grinding disks including acoarse profile grinding disk and a fine profile grinding disk that areeach configured to grind a spiral profile of the rotor including spiraltoothing in the rotor, each of the two or more profile grinding diskshaving a non-linear profile and being configured to be affixed andremoved from the grinding spindle; a control including a computerisedsystem, wherein the computerised system automatically controlsperformance of grinding operations to manufacture the rotor using atleast the first cylindrical grinding disk and the two or more profilegrinding disks; and controls switching between a first operating modefor grinding with the one or more cylindrical grinding disks and asecond operating mode for grinding with the two or more profile grindingdisks, wherein the grinding machine is arranged such that when switchingbetween the first operating mode and the second operating mode thegrinding machine removes the first cylindrical grinding disk from thegrinding spindle, and the grinding machine affixes the coarse profilegrinding disk or the fine profile grinding disk to the grinding spindle,during which the grinding machine does not unclamp the workpiece,wherein the control controls the grinding machine to perform acylindrical grinding operation with the one or more cylindrical grindingdisks that includes a first cylindrical grinding operation that includescylindrically grinding a first section on a first end of the workpieceto obtain a cylindrical clamping surface that is centered with respectto a centre line of the workpiece along a longitudinal axis of theworkpiece, wherein the control controls the grinding machine to performa second cylindrical grinding operation that includes cylindricallygrinding with the one or more cylindrical grinding disks a secondsection on at least a second end of the workpiece, the second end of theworkpiece being opposite from the first end of the workpiece, to obtaina cylindrical support surface that is centred with respect to the centreline of the workpiece along the axis of the workpiece, wherein theclamping system performs a first clamping of the workpiece, the firstclamping being an initial clamping of the workpiece, wherein the controlcontrols the grinding machine to perform a profile grinding operationthat includes the clamping system performing a second clamping of theworkpiece at the first end on the cylindrical clamping surface toprovide rotational support to the workpiece during the profile grindingto form the rotor body of the screw rotor by controlling rotation of theworkpiece about the longitudinal axis of the workpiece during theprofile grinding operation, wherein the control controls the profilegrinding operation to include a first profile grinding operation thatincludes a first coarse profile grinding operation using the coarseprofile grinding disk to obtain a coarsely finished spiral toothing onthe spiral profile of workpiece, wherein, after said first profilegrinding operation, the control controls the grinding machine to performa third cylindrical grinding operation that includes grinding said oneor more rotor shaft sections or grinding an end face of the rotor body,wherein after said third cylindrical grinding operation is performed,the control controls the grinding machine to perform a second profilegrinding operation that includes finely grinding the profile of therotor body using the fine profile grinding disk during a fine profilegrinding operation to obtain a finely finished spiral toothing on thespiral profile of the workpiece, and wherein providing said rotationalsupport to the workpiece during said one or more profile grindingoperations includes driving the workpiece around the axis of theworkpiece by a clamp clamped at said cylindrical clamping surface duringsaid first profile grinding operation and during said second profilegrinding operation.
 2. The grinding machine according to claim 1,further comprising one or more deburring brushes, wherein the controlcontrols the grinding machine to switch to an additional operating modefor deburring the workpiece with a deburring brush.
 3. The grindingmachine according to claim 2, further comprising an automatic toolexchanger that contains a magazine with exchangeable grinding disks,wherein, during the manufacture of a rotor, one or more exchangeablegrinding disks from the magazine can be put on one or more universalgrinding spindles of the grinding machine.
 4. The grinding machineaccording to claim 3, wherein the magazine of the tool exchanger alsocontains one or more of said deburring brushes that can be put on one ormore universal grinding spindles of the grinding machine.
 5. Thegrinding machine according to claim 3, wherein the control controls theuniversal grinding spindle or universal grinding spindles as well as thetool exchanger.
 6. The grinding machine according to claim 1, furthercomprising one or more task-specific grinding spindles that each have aspecific grinding disk, a cylindrical grinding disk, or a profilegrinding disk.
 7. The grinding machine according to claim 6, furthercomprising one or more separate deburring brushes arranged on adeburring brush spindle.
 8. The grinding machine according to claim 6,wherein, during the manufacture of a rotor, the control is configured tocontrol the task-specific grinding spindle or task-specific grindingspindles without a specific grinding disk being exchanged on itstask-specific grinding spindle.
 9. The grinding machine according toclaim 1, further comprising a flushport or a set of flushports.
 10. Thegrinding machine according to claim 1, further comprising one or morepositionable and/or exchangeable flushports or sets of flushports thatare controlled by the control.
 11. The grinding machine according toclaim 1, wherein the non-linear profile of at least one of theinterchangeable profile grinding disks is a curved profile.
 12. Thegrinding machine according to claim 1, wherein the non-linear profile ofat least one of the interchangeable profile grinding disks is anon-rectilinear profile.
 13. The grinding machine according to claim 1,wherein at least one of the interchangeable profile grinding disks is aworm grinding disk.
 14. The grinding machine according to claim 1,wherein at least one of the interchangeable cylindrical grinding diskshas a rectilinear profile.
 15. The grinding machine according to claim1, wherein at least one of the interchangeable cylindrical grindingdisks has a stepped profile.
 16. The grinding machine according to claim1, wherein the grinding machine is configured such that during at leasta portion of the cylindrical grinding operation the axis of rotation ofthe interchangeable cylindrical grinding disk is at an oblique anglewith respect to a surface of the workpiece to be ground during saidportion of the cylindrical grinding operation.
 17. The grinding machineaccording to claim 16, wherein said oblique angle is 30°.
 18. Thegrinding machine according to claim 1, further comprising a support stayconfigured to support the workpiece during at least a portion of thesecond operating mode.
 19. The grinding machine according to claim 18,wherein the support stay is configured to be affixed around acylindrical support surface of the workpiece to support the workpiece ina rotating way.
 20. The grinding machine according to claim 1, whereinsaid clamping system includes a first center point clamp and a secondcenter point clamp configured to respectively contact a first centerpoint at a first end of the workpiece and a second center point at asecond end of the workpiece and clamp the workpiece therebetween, thesecond end of the workpiece being opposite from the first end of theworkpiece, and the clamping system further includes a clamping mechanismconfigured to contact an outer circumference of the workpiece.
 21. Thegrinding machine according to claim 1, wherein the control of thegrinding machine controls manufacturing of a male screw rotor and acomplementary female screw rotor, wherein each of the male screw rotorand the female screw rotor are manufactured in the grinding machine bychanging an orientation of profile grinding disks of the same singlegrinding machine.
 22. The grinding machine according to claim 1, whereinthe third cylindrical grinding operation includes grinding said one ormore rotor shaft sections.
 23. The grinding machine according to claim1, wherein the third cylindrical grinding operation includes grinding anend face of the rotor body.